Trunk-circuit.



H. D. CURRER.

TRUNK CIRCUIT.

APPLICATION FILED JUNE n. 1915.

Patented Oct. 29, 1918.

TIL/E2775?! Efamflfurr z'En of. Illinois, useful Improvements in Trunk-Circuits, of

- in a HIRAM n. CURRIER, or CHICAGO, rumors, assisnon'ro KELLOGG SWITCHBOARID AND SUPPLY COMPANY, or CHICAGO,:ILLI1\TOIS, AconronATIon or ILLINOIS.

- TRUNK-CIRCUIT, I

aassaoo;

7 "Specification of Letters Patent. rammed (Bot, 29, was,

Application filed .iune 11, 1915.- Serial No. 33,428.

To all whom it may concern:-

' Be it known that I, HIRAM D. CURRIER, a citizen ofthe United States of America, residing in Chicago, county of Cook, and State have lnvented certain new and p which the following is a specification. My invention relates to telephone systems,

and has to do more particularly with trunking systems in which calls are extended from the calling substation through operators cord and trunk circuits to called substations, an object of my. invention-being to provide an improved system of the above character.

The general practice ofhandli-ng trunk calls in multi-exchange systems ,is to have an operator commonly known as an A-operator, answer the incoming calls by means of an OPGIZttOflS-COId CII'CUlt, and then in case of a trunk call, to communicate-with a trunk or B-operator in the desired exchange by means trunk to the called line.

whereby of order-wires which are independent of the trunk circuits, the so-called A-operator then connecting to an assigned trunk leading to the desired exchange which has been assigned by the trunking operaton, whereupon the trunk operator -extends the assigned This method of trunking calls requires special trunking operators and special trunking positions at a multiple switchboard. Systems of the abovedescribed character have been found faulty due to the stacking up of calls at a B or 'tr'unk opera'tors posltion, and to overcome this objection, I provide circuits in which the A-operator in addition to the usual answering and multiple jacks has trunk jacks accessible from her position extending to different exchanges and terminating at plugs before A operators in such exchanges so that each operator has both outgoing and incoming trunks. Each trunk is preferably 'mul-' tiply connected to a number of such trunk jacks whichare distributed among the dif-' ferent operators, positions and I also pro. vide busy indicating means in connection fi with each trunk jack in the form of a visual signal which indicates when such trunks are in use and with this arrangement the trunk calls are evenly erators. --I also provideja" control circuit when an operator is busy putting up a connection either in the nature of a ing drawing in heavily marked conductors. .ing end of the cord circuit distributed among the oplocal connection or a trunking connection,

all trunks which terminate at her position indicate busy at the outgoing jack ends. A.

feature of my invention is the provision of a control circuit, which operates means erator being indicated busy until she has ex-- tended the connection that she is handling to the called line, cuit restores making the trunk circuits associated with her posltion available for establishing further connections. There are other features of my invention and ,-these will be more particularly referred to in the following specification and-appended claims.

I For a better understanding of my invention reference maybe had to the accompanywhich a calling substation A and a calledsubstation D are shown terminating in the line circuits L and L, respectively, at difierent exchanges, together with an operators cord circuit B and a trunk cir-- cuit O. Substations A and D are of the well-known type, terminating in the lineciris provided for each jack-so that when a call is initiated over any line all of the line signals will be lighted, and any one'of a plurality of operators may seize the calls when the said control cir- The cord circuit B comprisesthe usual sWering plug AP and calling plug GP, the

two plugs being conductivcly united by the At thean'swer- B, I provide a high resistance test relay TE which is operated when. an answering plug is inserted into the jack of the calling line, whereby the answering'sleeve .supenvlsory relay AS is .'connected with the sleeve conductor through the alternate contact of the relay TE. The

rst 'operatorto answer the call seizes it to the exclusion of others, thatis, upon the insert1on of the first plug AP, into. the jack of a calling line, the therewith is connected and should a seize the call,

relay AS associated to the sleeve strand the relay TE of the second second operator attempt to A cord cannot operate and this preyents the should the said calling subscriber recall, the

removal of his receiver will again light the signals S so that the recall may be seized by the same or another operator. The calling end of the rd circuit D is provided with a calling sleeve supervisory relay CS and a calling tip supervisory relay CT. 7

To provide automatic party line ringing, I show a party line key BK and-a ringing control relay CR, the'said relay being energized when ringing key BK is actuated to close an energizing circuit for a ringing interrupter RI, which alternately connects ringing current to the called line, due to the interruption of the interrupter I. A call meter is provided comprising a meter relay MR and a meter magnet MM. Automatic listening and disconnect is also provided, the operators 'set 0 being connected to the cord circuit B upon the energization of the relay AS and disconnected from the cord circuit upon the energization of the relay GS of the calling end of the cord circuit.

In order to handle recalls and trunking connections, I provide a two-way key comprising the recall contacts RE and the orderwire contacts OW. The key when thrown in a direction to operate the contacts RE connects the operators set 0 with the cord circuit B and at the same time restores the link disconnect relay LD, and when the sa-id key is thrown in the opposite direction to operate the orderwire contacts OW, the talking conductors of the cord circuit are opened and then the operators set 0 is connected with the calling end of the cord circuit B whereby the operator at the said cord circuit B may converse with the operator to whom the trunk connection is being extended.

Now as to the trunk circuit C, I provide a number of multiply connected trunk jacks TJ for each trunk and distribute these jacks among the difi'erent operators positions and above each jack I show a busy signal BS,

-which is lighted when the trunk circuit C is in use, so that noother operator will attempt to connect'therewith. I provide two relays at the outgoing end of the trunk for controlling the signals BS, the said relays comprising a cut-ofl relay- CD and a line relay LR When an operator connects with a trunkjack TJ, its associatedcut-oif relay CO is operated over the sleeve strand and this lights all of its associated busyv lamps BS. I also show a repeating coil RCfor the trunk circuit C and a high resistance bridge relay H which relay is of high enough resistance to prevent theactuation of the tip relay CT of the cord circuit B.

When an operator inserts a plug CP into the trunk jack TJ, rela lowed by the operation ot the operators cutofi relay OC and the relay 0C the relay 00 operating to connect the distant trunk operators telephone set 0 to the trunk circuit and also operates to close a circuit for the combined guard and disconnect lamp GD, which remains lighted until the trunk lug is inserted in the jack of the called line.

pon connection of distant operators telephone set 0 the operators busy relay BO energizes to connect ground to all of the trunk busy control relays TBC of the idle incoming trunks terminating at this distant operators position, which ground connection serves to operate the said relays fol lowed by the operation of the line relays LE of these trunks. The said line relays operating close circuits throughtheir associated busy signals BS. The operation of relays TBC- also opens the circuit for the re lays H of the trunk circuits associated with the operators position so that no originating operator can converse or connect to any of the trunks extending to this busy operators position. And should an operator connect to this busy distant trunk operator, no circuit will be established for the relay H due to the interrupted circuit of relay H at the open contacts of the relays TBG. Also the instant that an operator answers a call by connecting an answering plug AP .toa calling line, all idle incoming trunk circuits terminating at -her position are rendered inoperative or busy by-the actuation of trunk busy relay B0 followed by the actuation of relays TBC. This busy condition is maintain'ed until the operator has extended a call by inserting the trunk plug TCPinto the line jack of the wanted line. In connection with trunk busy relay BO, the conductor H energizes folleading from its alternate contact 29 is com- I mon to all of this operators trunk circuits. That is, there is a connection 30 extending from the alternate contact 29 of relay B0 to the normal contact 33 of each of the rela s DC of this operators trunks and it I will thus be seen that no matter which one of her trunks is seized, all of the idle ones terminating at her position are maintained busy as long as the relay B0 is energized.

As each operators set is common to both the cord circuits B and the trunk circuit C at "the position, it is seen that its associated busy relay energizes each time a link circuit 1s used, energizing when the incoming end of the link is connected with acalling line and a v end the link or trunk is connected with a morejcontactsto ,be' controlled than good 1 vention as illustrated 'in thea practice will permit to he placed upon a sin- 7 [11 RT is also. provided as ,isjialso automatic le relay; :A'jtrflhk supervisory relay party line rin 'ng, an this end I provide a ri ging keyv K gand a control relay ROB energizedwheii; rmgin key is 'ac- -tuated;, =;hg trunks inte er re ay TIR is 'alsorprovided -being fadapted to alternately connect ringing.currcnt" of-the Maxine to the v Interruptions of the trunk. interrupterTL; QT-"also show a' meter no e ice consistmg'of ameter-magnet l li a in'eter relay m and 1 oit elfindetail my inaccom anying the su scriber drawing,fijand that at the substationA Wishes to. converse .With the's'ubscriberl at substat1on D,'located at a difierent'cxcliange, the subscriber'at the subz stati'on A -removes his receiver from the line relayf t o light the,line signals s. One ofa plurality of operators seizes the calhin. response to the lighted signals by inserting an answering plug" AP into the jaokJ of'the calling line. The insertion of the'answering plug AP intoithejacl: J

connects the cut-offrelay C0 of the-line circuit Land the high resistance test relay TE of thecord-jicircuit B in series circuit.

All) resistance pfqs'aid test relay TE. The test" relay sleeve superyisory relay AS to'jthe sleeve conductor-off the cord circuit B through the "eas mearea o e y The high resistance test relay TE operates but the cut-ofi relay does not due'to the high operating connects the answering vTEL-. RelayAS and relay-QQnow-operate in series, the circuit from battery through the winding of-the -relay AS, the aItern'ate contact: 1 of the "relay! TE, normal contact 2 of relay LD the sleeve contacts of the connected pliigan'd jack through the .Winding' of the ,cut-ofl' relay CO ground. The

- groimdthrough relay CO, the relay TE be 1ng shimte'd= out by relay AS, restores to normal, The relayCOoperating opens the -energizing'oircuit of the line relay LR, the

linefrelay. LR restoring brings about the efiacement'of theline signals S. The relay AS upon energizin'g'closes its alternate contacts 3 and 4- ,to connect the operators set 0 to the cord circuit B through the said alternate contacts 3 and 4 of the, relay AS,

ftolthe' tip conductor fleeting the operation of the relay :then closes a locking circuit for v relay CS. The insertion and the normal contacts5 and 6 of the calling sleeve supervisory relayCS of the cord circuit B. Upon the connection of the operato'rs set to the link circuit the operators relay BO energizes and places a busy poten- -t1al upon all the idle operators link and trunk circuits associated with the operators set O. y n Before describing the further operation of the system. illustrated, I will describe briefly calling line after the first operator has inserted the plug, AP, the second operators set will not be connected to the calling line due to the failure of the test relay TE of the second cord circuit to operatebecauseof the parallel circuit established through the low reslstance sleeve supervisory relay AS ot the firstcord circuit, therefore the relay TE of the second cord does not operate,

thus failing to connect the operators set of the second cord circuit and the said operator receiving no response knows that the call has-been seized and withdraws the plug from therconnecte'd jack.

Again taking up the connection, the op? erator now asceftains the Wants of. thehall- 'ing subscriber and finding that the wanted line terminates at a distant exchange, in-

serts the callingplug GP into an idle trunk jack TJ leadinglto the wanted exchange, which idle trunk etfaced busy-signals BS. The insertion of the plug GP into the trunk jack TJ closes jack is indicated by the.

a seriesenergizing circuit for the relay CO and the sleeve supervisory relay CS, said circuit being traced from'battery through the winding'of the relay CS, sleeve contacts of the connected plug, and jack through the Winding of the cut-ofl' relay ,CO toground. The cut ofl frelay CO upon energizing, closes its alternate contact 7, thereby bringing-about the lighting of all of the busy signals BS associated with the jacks of this connected trunk, and also efl'ecting the continuity of the sleeve conductor of the trunk.

The relay CS, upon energizing, opens its normal contacts 5and 6, disconnecting the operators set 0 from the cord circuit, and also closes an energizing circuit for the calling supervisory lamp CL traced from battery through the said lamp, normal contact 8 of relay RCR, normal contact 9 of relay CT, to ground at alternate contact 10 of of the plug CP lnto the trunk jack TJ establishes a series c rcuit for the-relay CS and CT of the cord circuit B andthe high resistance trunkrelay H, the circuit being traced from battery through the winding of relay GS, sleeve contacts of the connected plu and jack, the alternate contact 11 of relay O conductor BO operatesbut being of a comparatively 12, the winding 13 of the repeating coil RC, the normalcontact 17 of relay TBC, the winding of. relay H, the winding 14 of the repeating coil, RC, conductor 18, the tip contacts of the connected plug and jack, the alternate contact 19 of relay CS, normal contact 20 of relay IR, through the winding of relay CT to ground. The relay CS of' the cord circuit B and the relay H of the trunk circuit C are energized, but due to the high resistance of the relay H of the trunk circuit C, the calling tip supervisory relay CT of the cord circuit B fails to energize thereby permitting the supervisory signal CL to remain lighted until the called subscriber of the substation D answers.

The relay H having energized now closes a circuit for the relay 0C, this circuit being traced from battery through Winding of relay OC to ground at alternate contact 21 of relay H. The relay ()0 is also energized upon the actuation of the relay H, thecircuit being traced from battery through the Winding of-the said relay to ground at alternate contact 21 of relay H. The relay OC operating, closes a circuit for the combined guard and disconnect signal GD,

traced from battery through the lamp GD, alternate contact 23 of relay 0G to ground at normal contact 24 of relay TS The closing of alternate contacts 25 and 26 of relay 00 connects the operators set 0 through normal contacts 27 and 28 of relay TS to the trunk talking conductors. The closing of alternate contact 26 of relay OC establishes an energizing circuit for the operators busy relay B0 the circuit being traced from ground through the winding of relay B0 alternate contact 26 of relay OC, normal contact28 of relay TS, through the winding of relay TS to battery. The relay high resistance does not permit the relay TS to energize. The relay B0 upon energizing closes its alternate contact 29 connecting ground to its common conductor-'30.

The conductors 30 which extend to the idle trunks of this operators position cause the I operation of the trunk busy control relays TBCassociated with such idle trunks. The

energization of the relays TBC of such idle trunks establishes a circuit for the busy signals BS associated with the jacks of such idle trunks due tov the closure of their alternate contacts 31. The busy indication serves to keep other operators from extending connections to thisbusy operator.

It is desirable when the trunk operator is answering this trunk call to keep other operators from'extending trunk connections to her position. The operation of the trunk busy control relays TBC opens the circuits of the relays H, and even should another operator connect to this trunk operators position, she will not be able to converse with the trunk operator due to the failure of relays OO and H to operate to associate the operators telephone set with. the calling relays LE of these. trunk circuits, the circuit being traced from battery, throughthe alternate contact 31 of relays TBC,'normal contacts 34 of relays 0C the windings 13 of the repeating coils RC, sleeve trunk conductors 12, normal contacts 11, the windings of relays LE the tip trunk conductors 18,

the windings 14 of repeating coils R0 to ground at alternate contacts 35 of relays TBC. The relays LE of these idle trunks operate closing their alternate contacts 36 to light their associated busy signals BS. Should another operator insert a plug into a trunk jack associated with this busy trunk operators position, even though the busy signals BS are lighted, the second A-operator will receive no response as the circuits of the relays H are open at contacts 17 of relays TBC. The second A-operator receiving no response, knows that the trunk opera tor is busy setting up a connection and withdraws the plug from the trunk jack. It will thus be seen that no two A-operators can connect to the same trunk operator at one time. With this arrangement it will be seen that the calls are not stacked up at one trunk operators position but are distributed among the idle trunk operators so that all the work is uniformly distributed. The ground connection from alternate contact 29 of trunk busy relay BO does not affect busy trunks due to the fact that relays 00 of such trunks are energized and their normal contacts 34 are open. y

The operator'at cord circuit B having extended connection to the trunk circuit C now actuates the two-way key to operate the orderwire key OW, thus connecting her telephone set 0 with that of the'operator at the distant exchange, and to also openthe tip and sleeve conductors of the cord circuit B so that the calling subscriber does not TCP into the multiple jack J of the wanted Ill ' 38. Upon the energization of the relay TS position opening the circuit of the guard its normal contact 24 assumes its alternate signal GD and efiacing it. Upon the energization of relay TS, its normal contacts 27 and 28 are interrupted disconnecting the operators telephone set, and also eflecting the denergization of the relay B0 and thus removing the busy condition of allof the operators trunks. The relay BO restoring allows the relays TBC to deenergize to open the circuits of relays LE of all idle trunks, which relays in turn deenergize to extinguish the busy signals BS associated with said idle trunks. The normal contacts 17 of relays TBC again closing placing the relays H in operative relation with the idle trunk circuits. The operator now actuates the proper ringing plunger of the ringing key RK thereby connecting the proper generator frequency to the ringing conductor 87. The actuation of the plunger in its fully depressed position also efiaces the closure of the common end "spring contacts 40 and 41 thereby closing a clrcuit for the ringing control relay RCB traced from battery through the winding of the said relay, the alternate contact 41 of the end sprin contacts, the normal contact 42 of relay T T, conductor 43 to ground at alternate contact 24 of relay TS. ',Upon the pressure being released from the depressed key plunger the end springs restore to normal but a locking circuit for the relay RCR is established traced,

from .battery through its alternate contact 44, normal contact 42 of relay TRT, conductor 43 to ground at alternate contact 24 of relay T8 I also'show aservice meter,

said service meter being actuated when the end springs assume their alternate position.

' The meter relay MR is energized over a circuit'traced fr'om batterythrough the winding'of said relay, alternate contact 40 of the end springs of the ringing key,- normal contact 44 of, relay ROR normal contact '42, conductor 43 to ground at alternate contact 24. The meter relay closes its alternate contact 45, closing an energizin circuit for the meter magnet MM which is actuated to step the meter mechanism to register the established connection. The relay RCR upon energizingv closes an energizing circuit f r trunk interrupter relay TIR, said circuit, be-' ing traced from battery through the interrupter TI, winding of interrupter relay TIR, alternate contact 46 of relay RCR to ground at alternate contact 47 of relay ()0. The interrupter relay TIR is thus intermittently energized and d'energized due to the interruptions of the interrupter TI which intermittently connects the ringing conductor 87 to the alternate contact 48 of the interrupter relay TIR to ring the call bell at the called substation, the ringing'circuitbeing traced from the ungrounded pole of the generator, closed contact of the ringing key RK, alternate contact 48, tip contacts of the connected plug and jack, condenser and call bell at the called'substation, the sleeve contacts of the connected plug and jack, the alternate contact 49 of relay .TIR, through the resistance R to ground. Ringing current is thus intermittently transmitted to the calling substation D until the subscriber thereat responds.

Upon the response of the called subscriber at the substation D, an energizing circuit for the tip trunk supervisory TRT is established over a circuit traced from ground through the Winding of the said relay, the alternate I contact 50 of relay T8 normal contact 48, tip contacts of the connected plug and jack through the substation, sleeve contacts of the connected plug and jack, through the Wind ing of the relay TS to battery. Upon the operation of the relay TRT alow resistance. path is established for the relay CT of the cord circuit B over a circuit traced from ground through the winding of the relay CT, normal contact 20 of relay IR, alterf nate contact 19 of relay CS, tip contacts of the connected plug and jack, conductor 18, Winding '14 of repeatingv coil RC, alternate contact 51 of relay TRT, winding 13 of repeating coil RC, conductor 12, alternate contact 11 of relay CO sleeve contacts of the connected plug and jack and through the winding of the relay CS to battery. The relay CT of the cord-circuit B is thusenergized' opening its normal contact 9 to efi'ace the calling supervisory signal CL, notifylng the operator of the cord circuit B that the called subscribenhas answered. The low resistance path established forthe relay CT shunts out the relay H which relay restores to normal. The opening of normal contact 42 of relay TRT allows the relay RCR to restore and further operations of relay T113 are prevented due to the opening of contact a 46 of relay RCR The relay H restoring opens the circuit for relays OC and 0C but the said relays do not deenergize as an alter nate path has been established for them through alternate contact 42 of rela TRT. The calling subscriber at substat1on A and called subscriber at substation D are now in conversational circuit, the talking circuit being traced over the heavily marked conductors.

After completing conversation the subscribers replace their receivers upon their respective switch-hooks. The subscriber at the called substation D upon replacing his receiver upon the switch-hook opens the energizing circuit for the trunk tip relay TRT whereby the shunt is removed from around the winding of the relay H, relay H again energizes and due to its comparatively high resistance causes the restoration of the relay CT of the cord circuit B. The restoration of the calling tip relay CT of cord circuit B brings about the lighting of the calling supervisory lamp CL from battery through said lamp, normal contact 8, normal contact 9 to ground at alternate contact .10. The replacing 'of the receiver at the substation A brings about the restoration of the,

answering tip supervisory relay AT which closes a circuit for the answering supervisory lamp AL traced from battery, normal contact 55 of relay AT, the alternate contact 56 of relay AS to ground at alternate contact 10 of relay CS. The link disconnect relay being in multiple with the lamp AL also energizes when the relay, AT restores. The energization of the relay LD causes the disconnection of the link circuit at contacts 57 and 2 so that the subscriber at A can recall without awaiting the removal of the an.- sweringplug AP from the connected jack. The closing of alternate contact 58 of relay LD establishes a locking circuit for sleeve supervisory relay AS traced from battery,

through the winding of the said relay, alternate contact 58 of rela LD, alternate contact 56 of relay AS to ground at alternate contact 10 of relay CS. The locking circuit of the relay AS permits the continued energization of the said relay until the removal of the plugs from thelr respective jacks. The operator at the cord circuit B noting the two lighted supervisory signals AL and CL withdraws plugs AP and CP from their respective jacks. The removal of the plug CP from its connected trunk jack TJ allows the supervisor relay CS to restore to normal. The restoration of the relay CS brings about the interruption of its alternate contact 10 allowing the restoration of the relays LD, TE and AS so that the cord circuit is again at normal and available for other connections..

Upon the removal of the plug CP from the trunk jack TJ, the cut-off relay CO deenergizes but the busy signals BS remain lighted due to the operation of the line relay LR J The busy signals BS of this trunk are maintained lighted until the trunk calling plug TCP is removed from the jack of the called line. The withdrawal of plug CP from jack TJ allows the relayHto restore to relay TBC, normal cont-act 60 of relay 0C to ground at alternate cont-act 61 of relay TS The closing of the alternate contact 31 of relay TBC closes an energizing circuit for relay LR over the trunk conductors to ground at alternate contact 35, as previously described, the relay LR remaining energized until the trunk plug is withdrawn from the jack of the called line. The relay LR closing its alternate contact 36 brings about the lighting of the busy signals BS, thus indicating the busy condition of the trunk circuit C. Returning to the deenergization of the relay OC, the closing of its normal contact 23 brings about the lighting of the combined guard and disconnect lamp GD over a circuit traced from battery through the winding of the said lamp, normal contact 23, normal contact 42, conductor 43 to ground at alternate contact 24 of relay T S. The operator noting the lighted signal GD is aware that the plug G1 has been withdrawn from the trunk jack TJ' and now withdraws the trunk plug TCP from the jack of the called line. The withdrawal of the plug from the jack of the called line brings about the restoration of the relays TS and TS a-ndvthe restoration of the relay TS brings about the opening of the energizing circu1t of the relay TBC. The relay TBC restoring to normal opens the circuit of line relay LE and line relay I LR restoring, efi'aces the busy signals BS. The apparatus of the trunk C being at normal, it is not available for establishing other connections. a

From the foregoing it is thus seen that l have provided a. system wherein it. is impossible for more than one operator to effect connection with a trunk operators telephoneset at one time, even. though they should disregard the trunk busy signals and plug intoav jack connected to a trunk extending to the busy operators position in an effort to effect connection with the said operators telephone set. 1

While I have described my invention operating in connection with a certain circuit arrangen'lent ll do not wish to be limited to skilled in the art, therefore I do not wish to be limited to the exact structure as shown but am to cover all such changes and modi- 1,2 3,400 I I i ficationsthat come within the spirit and scope of the appended claims.

Having described my invention, what I claim as new and desire to secure byUnited States Letters Patent, is:

1. Ina multiple oflice telephone exchange system, a plurality oftrunk lines extending between ofiices, an operators telephone set adapted to be automatically connected to any of said trunk lines, andmeans for pre-, venting morethan one of said trunk lines from being connected to said telephone set at one time.

2. In a telephone system, a plurality of trunk lines extending to a distant ex change, an operators telephone set adapted to be automatically connected with any of said trunk lines, and means res onsive to such connection-forpreventing t e connection of other of said trunk lines to said operators telephone set.

3. In a telephone system, a plurality of trunk lines extending-to a distant exchange,

an operators telephone set adapted .to be automatically connected to said trunk lines, and means responsive to the connection of said telephone set to one of said trunk lines for rendering the remainder of said trunk lines inoperative. v i

1. In a telephone system, a plurality of link circuits and a" plurality of trunk circuits, an operators telephone associated with said trunk circuits, means responsive to the connection of oneof said link circuits with one of said trunk circuits for automatically 1 connecting said operators telephone to said trunk circuit, and means for preventing the" operative connection of said operators telephone with another of said trunk. circuits.

5. In a telephonesystem, a plurality of rlinkfcircuits, a plurality of trunk circuits,

an operators. telephone associated with said trunk circuits, means responsive to the connection of, one of said link circuits to one of said trunk circuits for automatically connecting the said operators telephone to said trunk circuit, and means for preventing the connection of said operators telephone with another of said trunk circuits if a second of said link circuits should be connected to a second ofsaid trunk circuits.

6. In, a telephone system, trunklines ex-' ltending from one exchange to a second exchange, terminals for each'end of said trunk 55 lines, an operators telephone set associated with the terminals at one end of sald trunk lines, means responsive to the seizure of'the terminal at the opposite end of one of said trunk lines for connecting said telephone set to said trunk line and for preventingv the operative connection of said telephone set with another one of said trunk lines.

7. In a telephone system, trunk lines extending from one exchange to a second exchange, terminals for each end pf said trunk lines, an operators telephone set associated 'Wlth the terminals at one end of said trunk lines, means responsive to the seizure of the terminal at the opposite end of one of said trunk lines for connecting said telephone set to said trunk line and for preventng the operative connection of said telephone set with another one of said trunk lines, and means for rendering said telephone set free upon the connection of said trunk line to a called line. a

8. In a multi-exchangej telephone system,-

trunk lines extending from one exchange. to a second exchange, an operators telephone set associated with said trunk lines and adapted to be automatically connected with trunk lines, and meansfor preventing the operative .connection of saidope'rators telephone set with more than onetrunk circuit at a time. I 9. In a telephone system an operators telephone set, trunk lines associated with said operators telephone set, means forseizing one of said trunk lines therebyautomatioally connecting the said operators telephone set with said trunk line, and means for preventing the operative connection of said telephone set with another of said trunk circuits while said first connection exists,

- 10. Ina telephone, system, an operators telephone set, link circuits and trunk circuits associated with said operatorfs telephone set, means for seizing one of sald link clrcuits thereby connecting said operators set with said link circuit, and means for preventing the operative connection of said operators set with one of said trunk circuits while said first connectiori'exists.

11. In" a telephone system, an operators telephone set, trunk circuits and link circuits associated with said "telephone. set,

means responsive to the seizure'fof -:o'1ne'of said link or trunk circuits for automatically --a second exchange, anoperators-telephone set at the second exchangeadapted-to be automatically connected and means responsive to the connection of said telephone set with one of said trunk lines for rendering the other of said .t

to said trunk lines,

lines busy and for rendering said operators telephone set inaccessible to the other of said' trunk, lines. I V

13. In a' telephone". exchan e'fsystem an operators telephone set, lin circuits, incoming and outgoing trunk circuits associated with the said operators telephone set automatic means for connecting the said operators telephone set to said linkwcircuits phone set to said outgoing trunk circuits,

and means responsive to said automatic means for preventing the connection of the said telephone set to more than one incoming trunk circuit at a time.

14. In a telephone system, an operators telephone, trunk circuits associated with the said operators telephone, a relay for said operators telephone common to said trunk circuits, a relay for each of said trunk circuits for preventing the connection of said telephone to said trunk circuits, and means responsive to the energization ofjsaid first relay for energizing the relays of said trunk circuits.

15. In a telephone system an operators telephone, trunk circuits and link circuits associated with said operators telephone, means for automatically connecting said operators telephone to one of said circuits, and means responsive to such connection for preventing said operators telephone from being connected to a second of said circuits.

16. A telephone system including an operators telephone, trunk circuits associated with said operators telephone, a relay for said operators telephone common to said trunks, a relay for each of said trunk circuits for preventing the connection of said telephone to said trunk circuits, and means responsive to an energization of said first relay to prevent energization of said trunk relays.

17. A telephone system including an operators telephone, trunk circuits associated with said operators telephone, a relay for said operators telephone, a relay for each of said trunk circuits, and means controlled b said first relay for preventing an energization of said trunk relays whereby said operators telephone is rendered inaccessible to the remaining trunk circuits.

18. A telephone system including an operators telephone, trunkcircuits associated with said operators telephone, a relay for said operators telephone, a relay for each of said trunk circuits, and means responsive to an energization of said first relay for pre-.

venting an energization of any of said remaining trunk relays thereby preventing the operative association of said operators telephone with any of said trunk circuits.

19. A telephone system including a plurality of inter-office trunk circuits, an operators telephone associated with said trunk circuits, means responsive to the connection of a link circuit to one of said trunk circuits for operatively connecting said operators telephone with said trunk circuit.

20. A telephone system including a plurality of inter-ofiice' trunk circuits, an operators telephone associated with said trunk circuits, means responsive to the connecsociated with said trunk circuits and adapt:

ed to be connected to any of said trunk circuits, and means for preventing the operative connection ofsaid operators telephone set to more than one of said trunk circuits at a time. i I

22. Atelephonesystemincludingaplurality of A operators connecting circuits, a plurality of trunk circuits for extending calls from A operators circuits to called subscribers lines, an operators telephone set, means for connecting saidoperators telephone set to each of said trunk circuits, and means responsive to the connection of said operators set to one of said trunk circuits to prevent its connection to another of said trunk circuits.

A telephone system including a plurality of connecting circuits, a plurality of operators trunk circuits for extending connections from said connecting circuits to called subscribers lines, an operators telephone, a relay for each of said trunk circuits, means controlled by each of said relays for connecting its associated trunk circuit with said operators-telephone, and means controlled by the operation of one of said relays to prevent the operation of another of said relays.

2 A telephone system including opera tors link circuits; operators trunk circuits; an operators telephone set associated with said trunk circuits; busy signals for said trunk circuits; means responsive to the connection of an operators link circuit to one of said trunk circuits for connecting said operators telephone to said trunk circuit, to operate the busy signals of said trunk circuits, and for preventing the connection of another of said link circuits to said operators telephone set via another of said trunk circuits.

25. A telephone system including operators link circuits, operators trunk circuits, an operators telephone associated-With said trunk circuits, means responsive to the connection of one of said link circuits to one of said trunk circuits to connect said operators telephone with said trunk circuit, and means for preventing the connection of other of said link circuits to said operators telehone as long as said operators telephone 1s connected to. said'first trunk circuit.

26, A telephone system including a plurality of A operators connecting circuits,

a plurality of B operators trunk circuits,

an operators telephone, a relay for each of sald trunk circuits for, connecting said operators telephone thereto, and means responsive to the operation of one of said relays for preventing the operation of another of said relays. I a

27. A telephone system including operators link circuits, operators trunk circuits, an operators telephone set associated with said trunk circuits, busy signals for said trunk circuits, means responsive to the connectipn of one of said operators link circuits 'to one of said trunk circuits for connecting said operators telephone to said trunk circuit, means also responsive to such connection for operating the busy signals of the other of said trunk circuits, and further means responsive to such connection for preventing the connection of another of said trunk circuits to said operators telephone set While said set remains connected to said first trunk circuit.

Signed by me atChicago, county of Cook and State of Illinois, in. the presence of two witnesses.

HIRAM D. CURRIER. Witnesses: 4 v

G. A. JoNocHoMnsKI B. OBRmN. 

